Analytical study of operating reactor noise on a single channel and a single phase flow model, 2

Analytical forms of the spatially distributed noise sources used in a companion study on their propagation (this journal, 10 [5], 259 (1973)) have been examined and determined. Nuclear noise sources can be regarded as white both in frequency and space. The thermal noise source due to the fact that heat energy is transferred with a definite magnitude at the transfer surface is also white. On the other hand, noise sources that are associated with fluctuations in the relaxation time constants of temperature are usually not white whether in frequency or in space. Their properties can be completely determined from the measured power spectral densities (PSD) of the fluctuations in coolant velocity and density, as well as from their cross PSD. The hydrodynamical noise is due to the random variations in the heat removal rate of the coolant and turns out to be non-white. The mechanical noise source is determined from the PSD of the statistical reactivity modulations caused by fluctuations in the fuel and control-rod positions.